Pad Mounted Xformer as Step upp transformer
Pad Mounted Xformer as Step upp transformer
(OP)
I need to step up a 2MW 480VAC standby diesel generator to 13.2kV in order to tie it into an existing 13.2kv system via and open transition MV auto transfer switch.
I also want to have this 2500kVA transformer available as a spare in the event one of the two normal source pad mounts should fail. Since the normal source transformers are 13.2kV/4800-277 D/Y with some 4 wire loads, I am thinking that the step up transformer will need to be wound Y/Y
Questions:
1. Is a pad mounted transformer suited for generator step up duty?
2. Are there any issues having a Y/Y step-up feeding a D/Y step down when the generator is in use and the utility is off.
3. Can the Y/Y replace the D/Y as the utility source step down in the event a D/Y fails?
4. I assume losses in the step-up step down scheme. Is there a factor to use to up size the generator in this application?
Any and all other comments on this scheme will be appreciated.
Thanks
I also want to have this 2500kVA transformer available as a spare in the event one of the two normal source pad mounts should fail. Since the normal source transformers are 13.2kV/4800-277 D/Y with some 4 wire loads, I am thinking that the step up transformer will need to be wound Y/Y
Questions:
1. Is a pad mounted transformer suited for generator step up duty?
2. Are there any issues having a Y/Y step-up feeding a D/Y step down when the generator is in use and the utility is off.
3. Can the Y/Y replace the D/Y as the utility source step down in the event a D/Y fails?
4. I assume losses in the step-up step down scheme. Is there a factor to use to up size the generator in this application?
Any and all other comments on this scheme will be appreciated.
Thanks






RE: Pad Mounted Xformer as Step upp transformer
2. Hard to say.
3. It depends on your grounding and protective relaying schemes. I wouldn't bet on it. The transformer configuration can completely change your protection requirements. Keep in mind the delta-wye has a 30 deg phase shift.
4. Losses would be at most a few percent. I would be more concerned about voltage regulation due to the increased impedance in the circuit.
Based on the number and type of questions, I'd strongly recommend hiring a licensed engineer to evaluate this before making any purchase decisions.
RE: Pad Mounted Xformer as Step upp transformer